Em Fri, Jan 06, 2012 at 09:46:29PM +0100, Adrian Knoth escreveu: > While playing with > > https://rt.wiki.kernel.org/articles/t/h/r/Threaded_RT-application_with_memory_locking_and_stack_handling_example_f48b.html > > I was wondering why pthread_create() should cause minor page faults when > there is a pre-allocated pre-faulted 100MB memory pool. > > Simply running the example causes roughly 30 minor page faults. When I > manually allocate stack memory for the stack (after mlockall() and > mallopt have been called) and use pthread_attr_setstack() before calling > pthread_create(), minor page faults drop to 2. > > Does anybody happen to know what is causing these remaining two page > faults? My only guess so far is kernel memory to hold some > organizational data for the new thread after clone() has been invoked, > but this could also be completely wrong. > > Note that I don't need to get page faults down to 0, I'm only looking > for an explanation to understand the issue at hand to confirm that > pthread_create() must not be used from an RT context. Try: $ perf record --event minor-faults --call-graph your-program $ perf report Should answer that question if running on a -fno-omit-frame-pointer binary world. Or at least provide the callchains for the kernel part of the call chains. 32-bit distros should be OK in that respect. - Arnaldo -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
